The present invention relates to a linear driving device and more particularly to a linear driving device having an improved clamping arrangement.
The document EP 1 118 796 B1 describes a linear winch or traction device having two caterpillars. One of these caterpillars is sliding relatively to the other one along a linear translation direction inclined to the axis of the pulled cable, so that the pulling onto the cable tends to move the sliding caterpillar towards the other one, to create a clamping force onto the cable. However, the disclosed arrangement is sensitive to dust, thus leading to the need of an adequate protection of the moveable parts, especially the sliding portions, so that cost and complexity will increase. Internal friction between the sliding parts will also decrease the efficiency of the device to create a clamping force from the pulling force, so that the reliability of the apparatus is questionable. Moreover, such winch is not adequate to pull a large variety of cables in terms of robustness. The magnitude of the clamping force is determined by the friction ratio (between the cable and sliding caterpillar), and the pulling force, in relation with the inclined slider. In other words, if some cables are too weak to resist to this non variable clamping force, it will be impossible to drive them without damage. The last concern with this winch is that it is impossible to drive the cable in two opposite directions (i.e. push-pull operations) without removing the cable out of the winch, turning the latter by 180° and reinstalling the cable between the two caterpillars to drive the cable in the opposite direction. This set up is long and reduces the overall operating availability of the equipment if numeral push-pull changes are required.